1. Field of the Invention
The invention relates to a technical field of flat displays and, more particularly, to an LCD panel driving method and device with charge sharing.
2. Description of Related Art
Current portable electronic products, such as PDAs, MP3 players and the like, are getting more and more popular with the development of the electronics industry. In general, the portable electronic products typically are equipped with a small-scale liquid crystal display (LCD), such as a thin-film transistor LCD (TFT-LCD).
FIG. 1 is a schematic diagram of a typical TFT-LCD panel. The panel includes four scan lines (SL1-SL4) 102, three data lines 104, twelve pixels 106, a gate driving circuit 108, a signal driving circuit 110, a common voltage driving circuit 126, three switches (SW1R, SW2R, SW3R) 112, a switch control circuit 114 and a common capacitor 116. Each pixel 106 has a transistor 118 and a capacitor 120 to store charges. Each data line 104 has parasitic resistors 122 and parasitic capacitors 124.
The ends of each capacitor 120 are connected to the respective electrodes at two ends of a liquid crystal (not shown). The transmittance of a liquid crystal is changed by changing the voltage stored in the respective capacitor 120. Further, each capacitor 120 has one end connected to a drain of a respective transistor 118 and the other commonly connected to a common voltage node Vcom, and the transistor 118 has a source connected to a data line 104 and a gate connected to a scan line 102. The panel is driven by first using the gate driving circuit 108 to send a switch voltage to the scan lines 102 in order to sequentially turn the transistors 118 on, then using the switch control circuit 114 to sequentially switch the switches 112 on, and finally using the signal driving circuit 110 to sent a voltage to the data lines 104 in order to charge the capacitors 120 through the respective transistors 118, thereby reaching a specific voltage.
To prevent a liquid crystal from being dissolved and becoming unusable, an alternating current (AC) power is typically used to drive an LCD. One well-known technique is the common voltage swing drive method. Namely, a voltage of each data line 104 is alternately higher and lower than a voltage of the common voltage node Vcom, and accordingly the liquid crystals receive alternate positive and negative driving of the AC to thus prevent a damage from being driven by a direct current (DC) voltage. FIG. 2 is a diagram of voltage waveforms of a data line 104 and the common voltage node Vcom. FIG. 3 is a flowchart of the common voltage swing drive method. FIG. 4 is a diagram of waveforms that are presented on nodes T1-T4 when using the common voltage swing drive method. As shown in FIG. 4, when the common voltage node Vcom is phase inverted, the signal driving circuit 110 requires driving the data lines to a target voltage, which consumes much power and has a very long rising time.